Daily methionine requirements of healthy Indian men, measured by a 24-h indicator amino acid oxidation and balance technique

Abstract

Background: The 1985 FAO/WHO/UNU upper requirement for the sulfur-containing amino acids in healthy adults, which was set at 13 mg·kg-1·d-1, is based on nitrogen balance studies in Western subjects. Short-term tracer-based studies also estimated a mean requirement of 13 mg·kg-1·d-1, but whether this estimate is applicable to healthy populations worldwide is unknown. Objective: Using a 24-h indicator amino acid oxidation and balance method with 7 test methionine intakes (3, 6, 9, 13, 18, 21, and 24 mg·kg -1·d-1), we assessed methionine requirements in healthy, well-nourished Indians. Design: Twenty-one healthy, well-nourished Indian men were studied during each of 3 randomly assigned 7-d diet periods in which methionine intakes (diet devoid of cysteine) were equally placed on either side of the putative mean methionine requirement of 13 mg·kg -1·d-1. Twenty-four-hour indicator amino acid oxidation and balance were measured on day 7 by using a 24-h [ 13C]leucine tracer infusion. The breakpoint in the relation between these values and the methionine intake was determined. Results: Two-phase linear regression of daily leucine oxidation against methionine intake estimated a breakpoint in the response curve at a methionine intake of 14 mg·kg -1·d-1 (95% CI: 11, 23 mg·kg -1·d-1). The breakpoint estimated from the leucine balance-methionine intake relation was 15 mg·kg -1·d-1 (95% CI: 11, 27 mg·kg -1·d-1). Conclusions: From the 24-h indicator amino acid oxidation and balance approach, a mean methionine requirement, in the absence of cysteine intake, of 15 mg·kg-1·d -1 is proposed for healthy, wellnourished Indian adults. This requirement is similar to that established in Western adults. © 2003 American Society for Clinical Nutrition.